Feeder device, feeded station and method of feeding

ABSTRACT

A device for continuous and individual feeding of sheets from a stack to a depositon site comprises gripping members ( 15 ) for grasping and hoding the sheets, and a movement device for displacing the gripping members ( 15 ) between the stack and the deposition site. The movement device displays two arms ( 12, 13 ), which are provided with the gripping members ( 15 ). The arms ( 12, 13 ) are pivotal about a vertical pivot axis ( 14 ) and are movable therealong in the verical direction to positions ( 33 ) for both depositing and picking a sheet. Further, the one arm ( 12, 13 ) may be pivoted past the other ( 12, 13 ). A feeder station for feeding in accordance with the foregoing includes at least one sheet stack, a deposition site and a feeder device. The stack and the deposition site are disposed on a common arc of a circle, and the feeder device has a pivotal arm ( 12, 13 ) which is provided with gripping members ( 15 ). A method of feeding in accordance with the foregoing in which use is made of a movement device as disclosed above. One gripping member ( 15 ) discharges a sheet when the second gripping member grasps a sheet on the stack. Thereafter, the gripping members ( 15 ) are lifted and pivoted so that they pass each other, whereupon they are both lowered, so that the method may be repeated.

TECHNICAL FIELD

The present invention relates to a device for the continuous andindividual feeding of sheet metal plates from a stack of sheets to adeposition site, and comprising a movement device for displacement ofgripping members which are designed to individually grasp and hold thesheets, between the sheet stack and the deposition site, and back.

The present invention further relates to a feeder station for thecontinuous and individual discharge of sheets and comprising at leastone, but preferably two stacks of sheets which are to be fed, adeposition site for sheets and a feeder device for the individualpicking of sheets and deposition thereof at the deposition site.

Finally, the present invention relates to a method of continuous andindividual feeding of sheets from a stack of sheets to a depositionsite, use being made of a movement device by means of which grippingmembers designed to individually grasp and hold the sheets move themfrom the stack to the deposition site.

BACKGROUND ART

In the mechanisation of presses or press lines, the individual sheetsare collected from a stack of sheets by means of some type of feederdevice which individually feeds the sheets to a centring device wherethe sheets are accurately positionally fixed and from whence they aresubsequently fed into the press. On condition that the position of thesheet stack is accurately known, the sheets can possibly be fed straightinto the press. Given that increasing mechanisation is taking place, ithas been possible to increase the capacity of the press or the pressline considerably in recent years. This implies that a feeding rate of30 workpieces/min is desirable, a level which today's technology cannotmeet using two picking stations.

Many press lines are obsolescent but have been gradually modernised.This often entails that the space ahead of the first press or betweenadjacent presses is extremely small, since presses were previously fedmanually.

A type of feeder device, the so-called dip feeder, displays a pattern ofmovement which implies that each end of a rectilinear movement isdownwardly directed.

In order to realise such a pattern of movement, complex mechanics arerequired with large, moving masses, from which it follows that themaximum workrate will be limited in the extreme. Consequently, a dipfeeder cannot be used when the requirement on capacity exceeds 15/20workpieces/min. If instead two dip feeders are employed whichalternatingly take sheets from a stack, there will be a break in thefeeding operation when the stack is consumed and must thus be replacedby a new stack. Such a production stoppage in a long, mechanisedproduction line cannot be accepted.

It has also been proposed that an industrial robot be employed for thefeeding of metal sheets. In order to meet the above-mentioned workratewithout stoppage on the replenishment of the sheet stack, four robotswould be required, which in turn requires a large space, entailing thatthe robots, for this reason alone, are unusable in most cases. Inaddition, the costs involved will be prohibitively high.

OUTLINE OF THE INVENTION

The present invention has for its object to design the feeder deviceintimated by way of introduction, the feeder station intimated by way ofintroduction, and also the method intimated by way of introduction suchthat sufficient capacity is attained, that the requirement on smallspace needs can be met and that continuous operation can be carried outfor lengthy periods of time, as well as that equipment employed canstand on the floor and costs can be kept within an acceptable ceiling.

The objects forming the basis of the present invention with respect tothe feeder device will be attained if this is given the characterisingfeatures as set forth in appended claim 1.

These characterising features afford the advantage that a high capacityis achieved in that both of the arms can operate alternatingly, smallspaces needs in that both of the arms pivot about a common axis,continuous operation in that the arms may be employed for thealternating picking of sheets from two different stacks, and finallythat the device may readily be placed on the workshop floor.

The objects forming the basis of the present invention with respect tothe feeder station will be attained if this is given the characterisingfeatures as set forth in appended claim 10.

As a result, the major advantage will be afforded that a feeder stationis realised with high capacity since it operates alternatingly to oneand the same sheet stack, space needs will be small since both grippingmember pivot about a common axis, and continuous operation can beattained in that two stacks can be processed alternatingly.

The objects forming the basis of the present invention with respect tothe method will be attained if this is given the characterising featuresas set forth in appended claim 12.

These characterising features afford the advantage of great rapidity bythe alternating employment of the two gripping members, the requirementon small space needs will be met by the concentric pivoting of thegripping members and continuous operation will be attained by thealternating processing of two different stacks.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

The present invention will now be described in greater detailhereinbelow, with reference to the accompanying Drawings. In theaccompanying Drawings:

FIG. 1 is a vertical side elevation of a feeder device according to thepresent invention;

FIG. 2 is a vertical front elevation of a feeder station according tothe present invention, the greater part of the frame and similarcomponents having been omitted for purposes of clarity; and

FIG. 3 shows from above and highly schematically a part of the feederstation according to FIG. 2.

DESCRIPTION OF PREFERRED EMBODIMENT

FIG. 3 shows a feeder station schematically from above. The stationincludes a first 1 and a second 2 stack of metal sheets 3 and 4,respectively. The sheet stacks 1 and 2 rest on pallets 5 and 6,respectively, which in turn rest on lifting tables 7 and 8,respectively. The lifting tables are arranged in such a manner that theygradually lift the sheet stacks 1 and 2 as these are consumed so thatthe height level of the uppermost sheet in each stack is alwayssubstantially constant.

The sheets 3 and 4 on the sheet stacks 1 and 2, respectively, are to befed individually to a deposition site 9 which is at the same heightlevel at the level of the uppermost sheets 3 and 4, respectively. Thesheet stacks 1 and 2, as well as the deposition site 9, are arrangedalong a common arc of a circle 10 where, in the illustrated embodiment,they have a 90° distribution. The centre of this arc of a circle carriesreference numeral 11.

In the region of the centre 11 of the arc of a circle 10, there isdisposed a movement device which will be described in greater detailbelow with reference to FIGS. 1 and 2, and which has a first or lowerpivotal arm 12 and a second or upper pivotal arm 13 which are providedwith gripping members (not shown in FIG. 3) for gripping and fixedlyretaining the sheets. Both of the pivotal arms 12 and 13 have a commonpivot axis 14 (FIGS. 1 and 2) which also coincides with a substantiallyvertical line through the centre 11 of the arc of a circle 10.

Both of the pivotal arms 12 and 13 are movable in the vertical directionalong a vertical line which coincides with the pivot axis 14 through thecentre point 11. In such instance, the first arm 12 is movable in thevertical direction from a deposition level for depositing a sheet on thedeposition site 9, the level 33 also coinciding with a level 33 forpicking a sheet at either of the two stacks 1 and 2. From this lowerlevel, the arm is movable in an upward direction to a highest level 32.Correspondingly, the second arm 13 is movable from a pick-up ordeposition level 33 for picking a sheet and for depositing it at thedeposition site 9. This picking or deposition level coincides with acorresponding level for the first pivotal arm. In the verticaldirection, the second arm is movable to a highest level 31 which islocated above the highest level of the first arm 12. By raising thesecond arm 13 to its highest level, the arms can be pivoting past oneanother also when a sheet is secured in the gripping members 15 disposedon the arms.

On operation of the feeder station, it may be assumed that the first arm12 is located in its deposition level at the deposition site 9 and thatthe second arm 13 is located in the picking position at the stack 1.When the first arm has deposited its sheet and the second arm hasgrasped a new sheet, both of the arms are raised to their respectivehighest levels 32 and 31. When the lifting operation is completed so farthat the sheets are free of the stacks 1 and 2 and peripheral equipmentsuch as separators 16, a pivotal movement may be commenced for both armsin opposite directions. Alternatively, the pivotal movement may beinitiated only when both arms 12 and 13 have reached their respectivehighest levels. After completed pivoting through 90° in oppositedirections, the arms have changed place so that the second arm islocated above the deposition site 9 while the first arm is located overthe stack 1. Thereafter, the arms are lowered to their lowerdeposition-or picking levels and the cycle is repeated.

When, for example, the first stack 1 is consumed, the arms 12 and 13 arepivoted to the second stack 2 for feeding sheets from this stack to thedeposition site. During the time this feeding takes place from thesecond stack, the first stack is replenished, for which reason nooperational stoppage need be feared when the stack is replenished. Oncethe second stack 2 has also been consumed, the arms 12 and 13 arepivoted back in order to feed sheets from the stack 1 to the depositionsite 9, during which time the second stack 2 is replenished. As a resultof the alternating cooperation of the arms 12 and 13 with the stack 1and the stack 2, respectively, the possibility for continuous operationis thus offered.

In one practical version, the deposition site 9 may consist of acentring device where the individual sheets are accurately positioned atknown positions in order thereafter to be transported to a press tool ina press line.

If the position of the two stacks 1 and 2 is accurately defined, thesheets deposited at the deposition site 9 can, in an alternativeversion, be transported directly further to a press.

FIG. 2 shows the feeder station according to FIG. 3 in slightly greaterdetail. In this Figure, the vertical line which passes through thecentre 11 of the arc of a circle 10 has been given reference numeral 14.Both arms 11 and 12 are shown in the same positions as in FIG. 3. Itwill farther be apparent that, at the free ends of the arms 12 and 13,there is disposed a frame or so-called headpiece which is provided witha number of gripping members 15 which, in the illustrated embodiment,consist of suction cups of rubber. In the Figure, both of the arms 12and 13 are also shown in their respective highest positions 32 and 31,respectively.

It will be apparent from the Figure that sheet separators 16 aredisposed adjacent the two stacks 1 and 2 and serve the purpose ofpreventing more than one sheet at a time from being grasped by thegripping members 15. It will further be apparent that the sheetseparators prevent an unduly early commencement of the pivotal movementsof the two arms, since, in such a case, the grasped sheet wouldotherwise come into contact with the separators and either wholly let gofrom the gripping members or at least be positionally offset in anunacceptable manner.

It will be apparent from FIGS. 1 and 2 taken together that the arms 12and 13 are, via quick couplings 17 and 18, respectively, each connectedto their pivotal shaft or rod 19, 20, respectively. The shafts 19 are 20are connected, by the intermediary of belt transmissions 21 and 22,respectively, each to their drive motor 23 and 24, respectively, for thepivotal movements of the arms 12 and 13. The shafts 19 and 20 have thevertical pivot axis 14 through the centre 11 of the arc of the circle 10as their centre line.

The drive motors 23 and 24, the belt transmissions 21 and 22, as well asthe shafts 19 and 20 are each disposed on their carrier device 25 and26, respectively (FIG. 1). The carrier devices display four roller units27 each, which are movable in a vertical direction along mutuallyparallel guide rails 28. The carrier devices 25 and 26 are movable inthe vertical direction along the guide rails 28 by means of drive motors29 and belt transmissions 30. In FIG. 1, reference numeral 31 relates tothe highest level that the second arm 13 can assume, while referencenumeral 32 relates to the highest level that the first arm 12 canassume. Reference numeral 33 relates to the common, lower level for botharms 12 and 13 and coincides with the level for picking a sheet from thestacks 1 or 2 and for depositing a sheet at the deposition site 9.

It will be apparent from FIG. 1 that the movement area of the second arm13 is approximately twice as large as the movement area of the lower arm12. As a result, if synchronous operation is to be possible, the secondarm 13 must move in the vertical direction approximately twice asquickly as the lower arm and consequently also undergo approximatelytwice as great acceleration. In one practical embodiment, the distancebetween the uppermost level 31 and the lowermost level 33 is of theorder of magnitude of half a metre. If the device according to thepresent invention, when the distance is, for example, 475 mm, is to beable to maintain a feeding rate of 30 sheets/min, a complete verticalmovement travel for the upper arm 13 must not take more time than 0.5sec. with 0.25 sec. acceleration and 0.25 sec. retardation. The maximumvertical speed will be 1.9 m/s, while the acceleration is 7.6 m/s².Since the moving masses are considerable (approx. 275 kg includingcarried sheet), it is possible—in order to reduce the power requirementsin the two motors 29—to employ balancing cylinders 34 for balancing theeffects of gravity on these masses so that the drive motors only needcater for the inertia forces.

According to the present invention, it is not necessary that thedistribution angles between the stacks 1 and 2 and the deposition site 9be exactly 90°. Thus, it is, for example in particularly cramped spaces,possible to reduce these angles, perhaps as far as 75°, depending on thedimensions of the sheets in relation to the arm length.

Nor is it necessary that the angles be equal if other circumstancesconcerning lay-out were to so require.

In a further alternative, the angles may be greater than 90°, even asmuch as 110°.

The only requirement on the position of the stacks and the depositionsite 9 is that they must lie on a common arc of a circle.

In yet a further modified embodiment, the pivot axis 20 for the upperarm 13 may be turned to face downwards and thus be arranged in the samemanner as the lower 19. In a further alternative, the lower pivot axis19 may be cylindrical and at least partly surround the upper axis 20.

Regarding the stacks 1 and 2 and the deposition site 9, it was disclosedearlier that, in the vertical direction, they are disposed on the samelevel 33. This is a practical measure and facilitates programming of thecontrol unit of the subject matter of the present invention. However, itis not necessary, but the stacks 1 and 2 and the deposition site 9 mayinstead be disposed at different levels, two on the same level, or allon three different levels.

1. A device for the continuous and individual feeding of metal sheetsfrom a stack of sheets to a deposition site, and comprising a movementdevice for displacement of gripping members which are designed toindividually grasp and hold the sheets, between the sheet stack and thedeposition site, and back, wherein the movement device has a first and asecond arm provided with the gripping members, said arms extending outfrom and being pivotal about a common, substantially vertical pivotaxis; and that the arms are movable therealong in the vertical directionto positions for depositing a sheet, to positions for picking a sheet,and to positions where the one arm may be pivoted past over the other.2. The device as claimed in claim 1, wherein the first arm is a lowerarm, while the second arm is an upper arm; that the upper arm has alarger vertical area of movement than the lower; and that the upper armhas a highest position which is located higher than the highest positionof the lower arm.
 3. The device as claimed in claim 1 wherein the armsare of equal length and have their gripping members placed in the samemanner.
 4. The device as claimed in claim 1, wherein the arms aresecured each in their rotary rod or shaft which are coaxial with oneanother and with the pivot axis, and also disposed the one over theother, the shafts each being journalled in a carrier device movable inthe vertical direction along a guide.
 5. The device as claimed in claim4, wherein a drive motor for pivoting the shafts is disposed on eachcarrier device.
 6. The device as claimed in claim 4, wherein the guideincludes mutually parallel guide rails, along which roller units may berun on the carrier devices.
 7. The device as claimed in claim 4, whereinthe carrier devices are carried by and drivable under the action of amotorised toothed belt arrangement.
 8. The device as claimed in claim 4,wherein the carrier devices are connected to balancing means forbalancing at least a part of their weight.
 9. The device as claimed inclaim 1, wherein the arms are reciprocally pivotal within a sector of atleast 90°, but preferably 180°.
 10. A feeder station for continuous andindividual discharging of sheets, comprising two stacks of sheets whichare to be fed, a deposition site for sheets and a feeder device for theindividual picking of sheets and deposition thereof at the depositionsite, wherein the sheet stacks and the deposition site are disposed on acommon arc of a circle; and that the feeder device has an arm providedwith gripping members and disposed to transfer, alternatingly from theone or the other stack of sheets to the deposition site and that the armbeing pivotal about a substantially vertical line through the centerpoint of the arc of a circle.
 11. A method of continuous and individualfeeding of sheets from a stack of sheets to a deposition site, use beingmade of a movement device by means of which gripping members designedfor the individual grasping and holding of the sheets, displace themfrom the stack to the deposition site, wherein a first and a secondgripping member are pivoted about a common pivot axis and are verticallydisplaced therealong so that: the first gripping member discharges afirst sheet on the deposition site and the second gripping member graspsa second sheet on the stack; the first gripping member is lifted to afirst level and the second gripping member is lifted to a second levelhigher than the first; the first and the second gripping members arepivoted in opposite directions so the second passes over the first; thefirst and the second gripping members are lowered for picking a thirdsheet from the stack and depositing the second sheet on the depositionsite, respectively; the first and second gripping members are lifted tothe first and second levels, respectively; the first and the secondgripping members are pivoted in opposite directions so that the secondpasses over the first; and the first and the second gripping members arelowered for depositing the third sheet on the deposition site and forpicking a fourth sheet from the stack, respectively, and so on.
 12. Themethod as claimed in claim 11, wherein the gripping members arereciprocally pivoted between the first stack and the deposition siteuntil the first stack is consumed and then reciprocally between thesecond stack and the deposition site, while the first stack isreplenished.